CIRCULAR 76 MARCH 1937 Cotton Spacing AGRICULTURAL EXPERIMENT STATION OF THE ALABAMA POLYTECHNIC INSTITUTE M. J. FUNCHESS, Director AUBURN C)HOOL OF AGRICUL1TR. ; A _ T Cotton Spacing mum yields is of considerable interest to farmers. The amount of vegetative growth made by individual cotton plants is markedly influenced by spacing. If the plants are closely spaced or if several plants per hill are left in chopping, the resulting stalks are small and spindling; whereas, plants widely spaced produce a larger and more bushy type of stalk. These differences in stalk growth have often led to erroneous conclusions regarding the amount of cotton produced by variously spaced plants. In order to study the effect of spacing on the yield of cotton, experiments were conducted at various localities from 1924 to 1935. In one experiment the effect of spacing on the size of boll and length and percentage of lint was also studied. It is the purpose in this circular to report the results of these experiments. GENERAL PLAN OF EXPERIMENTS THE PROPER spacing of cotton for the production of maxi- There are three possible ways in which the number of cotton plants per acre may be varied, any one or any combination of which may be employed. They are: variations in the width of rows; variations in the distance between hills; and variations in the number of plants per hill. Each of these methods of variation was employed in the experiments conducted. In all experiments the rows were accurately laid off at the proper distances and seed was planted under a marked wire. The plants were thinned by hand to the desired number per hill after they were well established. As a general rule no measures were taken to control the boll weevil. Variations in Drill Spacings With Constant Width Rows First Experiment.-This experiment was conducted on a sandy loam soil at Auburn over the six-year period 1924-1929. Cotton on different plots was spaced 6, 12, 18, 30, and 36 inches apart in 31/2 -foot rows with one, two, three, and four plants per hill at each drill distance. Each spacing was in duplicate on both fertilized and unfertilized plots. The six-year average yields of seed cotton produced in this experiment are presented in Table 1. The largest yield was produced when cotton was spaced 18 inches in the drill with either two or four plants per hill, and the two smallest yields were produced by the two extremes in spacing. The maximum difference in yields, in this experiment, as a result of spacing was approximately 250 pounds of seed cotton per acre. 1 The experiments herein reported were conducted by H. B. Tisdale, R. Y. Bailey, Fred The manuscript was preStewart, R. C. Christopher, J. P. Wilson, and J. T. Williamson. pared by E. L. Mayton. TABLE Number o6 plants per hill Fert.' .- Pounds of Seed Cotton per Acre Produced at Various Drill Spacings in 3/ Drill Spacing -- inches 24 18 Six-year average pounds of seed cotton per acre f ert.fet 493 516 488 466 UnFert.' 2 -Foot Rows. 6 12 30 36 - f ert. 527 464 428 381 Un F ert.' Un-g 487 518 478 485 Fet' er.1 f r. U Fert Fet1 848 983 1,006 1,070 f r. U- Fert' er. f ert. Un 1 2 3 4 1 1,042 985 909 834 998 1,037 994 996 963 1,083 1,045 1,083 931 1,059 1,082 1,039 461 507 525 477 419 454 499 480 832 979 988 992 422 465 467 415 Fertilized at the rate of 600 pounds of superphopshate, 300 pounds of nitrate of soda, and 50 pounds of muriate of potash per acre. 4 On fertilized or unfertilized plots satisfactory yields were produced when cotton was spaced 6 inches in the drill with one plant per hill, 12 inches with two plants, 18 and 24 inches with either two, three, or four plants, and 30 inches with four plants. As a whole, the largest yields were produced at the 18- and 24inch drill spacings. The effect of spacing on the size of boll, percentage of lint, and length of lint was studied in this experiment. For these studies 100 bolls were picked at random from each plot and from their total weight was calculated the number of bolls per pound. These separate batches were ginned on a small gin and the percentage and the length of lint were determined. The results of these studies are presented in Table 2. It will be seen that close spacing markedly decreased the size of bolls. In almost every instance, an increase in the number of plants per acre caused a decrease in the size of the bolls produced. At the closest spacing on fertilized plots ninety-four bolls were required to make a pound of seed cotton; at the widest spacing only seventy-three were required. These two spacings, as was shown in Table 1, produced almost identical yields but it required approximately one fourth longer to harvest the cotton from the closer spacing because of the larger number of bolls. Fertilization increased the size of bolls about 5 per cent. The results presented in Table 2 on the percentage of lint and the length of lint show that neither was significantly affected by variations in spacing. Second Experiment.-A second cotton spacing experiment which was somewhat different in detail from the one previously discussed was conducted on the Main Station at Auburn, on the Wiregrass, Tennessee Valley, and Sand Mountain Substations, and on the Prattville Experiment Field over the five-year period, 1930-1934. The plot treatments were identical at all locations. The soil types represented were as follows: sandy loams on the Main Station, Wiregrass Substation, and Prattville Field; fine sandy loam on the Sand Mountain Substation; and clay loam on the Tennessee Valley Substation. These types are representative of the most important cotton soils of the State. Since the 18-inch drill spacing with two stalks per hill produced the greatest yield in the previous experiment, this spacing was used on the check plots in this experiment. On other plots the hills were spaced 9, 18, and 27 inches apart in 31/2 -foot rows with one, three, and six plants per hill at each drill distance. Each plot received 600 pounds per acre of a 6-10-4 fertilizer. The five-year average yield at each location and the average yield of all crops at all locations, which is an average of twentyfive crops of cotton, are presented in Table 3. These results show that the yield of cotton was reduced at the very close or very wide spacings. It will be noted that on the three highest yielding plots the hills were spaced 18 inches in the drill Table 2.-The Number of Boils per Pound and the Length and Percentage Number of bolls 1 per of Lint of Cotton Produced at Various Spacings. Plot No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 1 Number of plants per bill 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Number inches hills apart in drill 6 6 6 6 12 12 12 12 18 18 18 18 24 24 24 24 30 30 30 30 36 36 36 36 Number of plants per acre 24,891 49,782 74,673 99,564 12,446 24,892 37,338 49,784 8,297 16,594 24,891 33,188 6,223 12,446 18,669 24,892 4,978 9,956 14,934 19,912 4,148 8,296 12,444 16,592 pound Percentage of lint Fertilized 38 38 38 38 38 38 38 38 38 38 37 38 38 38 38 38 38 37 38 38 38 38 38 38 Unfertilized 40 40 40 40 39 40 40 40 39 39 38 40 39 39 39 39 39 39 39 38 39 39 39 39 Length of lint 2 in 1/32 inch Fertilized 84 88 93 94 77 88 88 89 75 78 83 83 72 78 79 81 75 76 79 81 73 78 78 78 Unf ertilized 88 95 98 103 83 88 92 91 79 84 90 90 77 83 84 86 78 81 81 85 79 81 81 84 Fertilized 26 27 28 28 25 26 27 27 27 26 27 27 26 27 26 27 27 27 26 27 26 27 27 27 Unfertilized 28 27 28 27 27 27 27 28 28 28 27 29 28 28 29 28 28 28 29 28 27 28 27 27 01 ,,,,, Six-year average. 2 Three-year average. Table 3.-The Production of Cotton at Various Drill Spacings in Spacing Plot No. Inches hills apart 18 9 9 9 18 18 18 18 18 27 27 27 18 Number of plants per bill Number of plants 3 '/2-Foot Rows at Different Locations in Alabama. average 1930-1934' Pounds of seed cotton per acre __________Five-year ______Substations _____ per acre Main Station 1,098 1,109 1,043 1,029 1,138 1,084 1,134 1,083 1,142 1,083 1,157 1,116 1,103 i _____ Wiregrass 1,404 1,361 1,267 1,162 1,433 1,399 1,363 1,242 1,419 1,275 1,335 1,313 1,415 1,418 acre. Tennessee Valley 1,235 1,194 1,170 1,186 1,298 1,364 1,375 1,322 1,304 1,226 1,259 1,238 1,336 1,293 Sand Mountain 1,456 1,467 1,326 1,331 1,458 1,413 1,458 1,416 1,476 1,381 1,386 1,388 1,458 1,462 Prattville Field 1,004 976 882 771 983 1,023 961 865 943 992 957 881 978 977 Grand average of all crops 2 1 3 6 2 1 3 6 2 1 3 6 2 Average of check plots 1, 5, 9, and 13 1 1 2 3 4 5 6 7 8 9 10 11 12 13 16,594 16,594 49,782 99,564 16,594 8,297 24,891 49,782 16,594 5,532 16,596 33,192 16,594 1,239 1,221 1,138 1,096 1,262 1,257 1,258 1,144 1,257 1,191 1,219 1,187 1,258 1,254 1,120 fertilizer per Each plot received annually 600 pounds of a 6-10-4 with either one, two, or three stalks per hill. There was a difference of only 5 pounds of seed cotton per acre in the yields produced at these three spacings. These average results show that, if cotton is blocked in chopping to this approximate distance, which is about two to three hoe widths, from one to three plants per hill will produce the maximum yield in 3/2-foot rows. It is clearly shown that six plants per hill are too many since the smallest yield at each drill spacing was produced when this number of plants was left. There was some variation in yields produced at the 18-inch drill spacing at the different locations but as a whole this drill spacing was the most satisfactory. These results show that when cotton was spaced to give from 8,000 to 25,000 plants per acre the largest yields were obtained. Very close spacings tended to increase the percentage of cotton open at the first picking but due to the production of smaller bolls the labor in picking was increased. In connection with this experiment on the Main Station the spacings were duplicated on unfertilized plots and the results are in general agreement with those where liberal applications of fertilizer were made. Variations in Width of Rows In experiments at Auburn and on the Wiregrass Substation the effect of variations in the width of rows on the yield of cotton was studied. In these tests the number of plants per acre was held constant by inverse variations in the width of rows and drill spacings. Each spacing was duplicated under two conditions of fertilization; on the Wiregrass Substation 600 and 300 pounds per acre of a 6-10-4 fertilizer were used; at Auburn 600 pounds of 6-10-4 and no fertilizer were used. The width of rows was varied from 2 /2to 61/2 feet. The results, Table 4, show that the largest yields were produced in 21/2-, 31/2-, or 41/2-foot rows. When cotton was liberally fertilized there was very little difference, at either location, in the amount of seed cotton produced when the row width was varied from 21/2 to 41/2 feet. Where only moderate fertilizer applications were made the largest yields were produced in 21/2- and 3 1/2-foot rows, and where no fertilizer was applied decidedly the largest yield was produced in the narrowest rows. Three plots with row widths of 3 feet were included in the spacing experiment reported in Table 3. On these plots cotton plants were spaced 36 inches in the drill with one, three, or six plants per hill. The largest yield was produced by three plants per hill; this spacing gave 14,520 plants per acre and the yield was only 33 pounds of seed cotton per acre less than the highest yielding plot. The yield was considerably reduced when only one plant was left in hills 36 inches apart. Table 4.-The Production of Cotton in Various Width Rows at Two Locations. Width rows in feet 21/2 of WiregrassSubstation Main Station Pounds of seed Pounds of seed Number of cotton per acre 1 Number of cotton per acre 300 lbs. 600 lbs. Unplants per 600 ibs. plants per acre fertilized acre acre acre acre 6-10-46-10-4 6-10-4 31/2 41/2 51/ 61/2 20,027 20,027 20,027 20,027 1,046 1,055 1,026 977 683 559 511 472 16,000 16,000 16,000 16,000 16,000 1,262 1,274 1,248 1,213 1,141 1,025 1,047 765 749 902 1 Five-year average. 2 Three-year average. 3 Two-year average. A second experiment, in which the width of cotton rows was varied, was conducted at the Wiregrass Substation from 1933 to 1935. The number of plants per acre was held constant by variations in the distance between hills. The following average yields were obtained in this experiment; in 3-foot rows, 1,368 pounds of seed cotton; in 4/2-foot rows, 1,244 pounds; and in 6-foot rows, 1,161 pounds per acre. SUMMARY Experiments were conducted from 1924 to 1935 to study the effect of the spacing of cotton plants on the size of bolls, the length and percentage of lint, and yield of seed cotton. The results of these studies may be briefly summarized as follows: The yield of cotton and the size of boll were the only (1) factors studied which were affected by variations in spacing. (2) The yield of cotton was influenced by variations in the width of rows, in the distance between hills, and in the number of plants per hill. (3) Spacings which gave less than 8,000 and more than 25,000 plants per acre tended to reduce the yield. The size of boll was increased by wide spacings and (4) decreased by close spacings. The optimum spacing was practically the same on the (5) different soil types on which these experiments were conducted. RECOMMENDATION Based on the results of studies presented in this circular it is recommended that cotton be spaced 18 inches apart in the drill with from one to three plants per hill. The width of rows, where liberal applications of fertilizer are made, may vary from 21/2 to 41/2 feet. Under conditions of low fertility or where only moderate fertilizer applications are made the width of rows should not be more than 31/2 feet.